Predicting Pathogenicity of Mycotoxin Combinations

Dr. S. Haladi of Alltech Canada, in conjunction with scientists at the University of Guelph, Ontario, has introduced a toxicity index to quantify the predicted pathogenicity of combinations of mycotoxins which may be present in feed.

Published research generally reports on the effect of individual mycotoxins on performance parameters in monogastric species. Dr. Haladi and his colleagues have developed a method to evaluate the possible deleterious effect of multiple overlays of mycotoxins.

Based on a review of the literature it was possible to compile the LD50 values for individual mycotoxins. These are indicated in Table 1 for the most frequently encountered compounds. With respect to poultry, DON is regarded as the least toxic of mycotoxins and a value of 1 was assigned this contaminant. At unity, DON serves as the index for toxicity of other mycotoxins or their combination. The toxicity index for a specific mycotoxin can be multiplied by its concentration in feed and the resulting value can be expressed in comparison to DON to provide a measure of relative toxicity. Table 2 shows the toxicity industry for four frequently encountered toxins. Toxicity indices range from 1 for DON to 28.17 for T-2 toxin. The mycotoxin equivalence expressed in ppb is calculated from the toxicity index and the concentration in feed. Accordingly the mycotoxin equivalence values range from 609ppb for afltoxin B1 to 4,793 ppb if all four toxins are present in a feed sample at the concentrations as indicated.

Dr. Haladi considers that the model as presented can be used under practical conditions to determine the potential losses associated with multiple mycotoxin contamination. The magnitude of the index can be applied to justify inclusion of an effective binder to ameliorate the anticipated depression in growth rate, feed conversion efficiency or livability.

Table 1. LD50 values for mycotoxins in one-day-old broiler chicks.

Mycotoxin

LD50 (mg/kg)

T-2 toxin

4.97

HT-2 toxin

7.22

Neosolaniol

24.87

Diacetoxyscirpenol (DAS)

3.82

Deoxynivalenol (DON)

140.00

Ochratoxin A

2.14

Citrinin

95.00

Aflatoxin B1

11.50

Moniliformin

5.40

Source: Leeson et al., 1995

Table 2. Calculations of total poultry toxicity based on LD50 values for mycotoxins.

Mycotoxin

Concentration in feed, ppb

*Toxicity Index

**Mycotoxin equivalence, ppb

Deoxynivalenol (DON)

2000

1.00

2,000

Aflatoxin B1

50

12.17

609

T-2 toxin

50

28.17

776

HT-2 toxin

40

19.39

4,793

*LD50 value of the least toxic mycotoxin divided by LD50 value of the mycotoxin in question
**Concentration in feed (ppd) multiplied by Toxicity Index